textproduct: Quad Cities

KEY MESSAGES

- More very humid and uncomfortable conditions for Wednesday, but cloud cover and precipitation may go against the need for a Heat Advisory.

- A Marginal, level 1 out of 5, risk for severe storms continues for tonight. The most likely time frame is 10 PM to 4 AM with damaging winds and hail being the primary risks.

- Wednesday and Thursday still look to be a stormy period with several rounds of strong to severe storms possible. There is an Enhanced, level 3 out of 5, risk for severe storms for both days and covering most of the local area. Locally heavy rainfall and flooding also possible.

SHORT TERM /THROUGH WEDNESDAY NIGHT/

Issued at 241 PM CDT Tue Jun 9 2026

Tonight...Will let the heat advisory ride, although cloud cover/debris has so far made widespread 100+ heat index readings limited so far. But there may be a late afternoon temp surge with VIS satellite showing more insolation occurring. MCV-driven isolated showers and storms may linger in the far southeast through early this evening. Otherwise will have to watch for a developing 25-30 KT southwesterly LLJ to possibly produce a broken line of mainly elevated warm air advection(WAA) wing storms later tonight and into early Wed morning. This feature may be connected to a MCS moving northeast acrs the central/northern MO RVR Valley and into MN. These storms if they can become a little more organized may be able to produce marginally severe hail overnight, with a wet microburst a secondary concern. Low temps generally in the lower 70s, and will bank on more of a southerly sfc wind increase to keep widespread fog development at bay.

Wednesday...A potentially messy convective period with a couple of rounds of storms possible making for plenty of uncertainty as one episode is going to effect the other and the models will have trouble following up after the results. As an upper ridge lobe pulls away, cyclonic southwesterly steering flow sprawls out acrs the region and a sfc cold front organizes early in the day acrs the MO RVR Valley. The majority of the recent CAM runs and some deterministics suggest a lead vort lobe or MCV-type feature to roll in from the west and kick up clusters of showers and thunderstorms acrs the area from late morning through at least mid afternoon.

Vertical kinematic and thermodynamic profiles suggest that this midday round may be marginally severe with all threats possible. Behind that wave, it will be up to gusty southwesterly sfc winds and cloud debris clear off to see how much the atmosphere can recover ahead of the incoming cold front that will look to move acrs the area from the west later in the evening. Increasing mid to upper jet dynamics and effective shear profiles(50-60 KTS) are favorable for supporting severe storms, especially more discrete supercell development late afternoon and early evening possibly right overhead of the local area.Several CAM runs show explosive development Wed evening, but this is in a re-charged air mass with 3000-4000 MUCAPEs. If we get the midday to early afternoon activity, there is some uncertainty that we will be able to re-charge a worked over air mass that quickly. But if indeed we manage to spawn new evening activity, large hail and tornadoes would be very possible. A farther west in central to western IA development may make the area susceptible to an organized maturing QLCS with damaging winds(possibly 70-80 MPH) the most widespread threat, as well as meso vortices tornadoes. Although the storms may be more progressive limiting residence times, 1.9 to 2+ inch PWATs would still support a flash flood risk in areas that receive repeated activity.

The latest wave/vort ensembles suggest even another vort max or MCV to roll out acrs the MO RVR Valley again late Wed night, with some potential of associated WAA wing of elevated showers/storms clipping parts of the northwestern CWA late Wed night into early Thu morning.

With convective debris, storm outflow and precip outright making for high temp uncertainty on Wednesday, will hold off on any heat headlines for tomorrow for now. Although there may be a few isolated pockets of 100+ degree heat index readings, 95 to near 100 may be more widespread. Still uncomfortable, but not dangerous.

LONG TERM /THURSDAY THROUGH MONDAY/

Issued at 241 PM CDT Tue Jun 9 2026

Thursday...Another shortwave trough embedded in the longwave over central Canada ejects into the Northern Plains, setting up a 120- knot jet streak across the Upper Mississippi River Valley. West- central Iowa will fall underneath the right entrance region of this jet streak and enhance the ageostrophic divergence over this region, supporting a deepening low pressure over Kansas. Two rounds of thunderstorm development appear likely Thursday: one in the morning along the transitioning warm front from Wednesday's convection and another one in the afternoon/early evening with the trough and cold frontal passage.

Looking at the instability Thursday morning, SBCAPE values could possibly (30-40%) exceed 2000 J/kg right along the warm front near Highway 30. This overlaps with 40-45 knots of westerly sfc-to-500 mb bulk shear which will be parallel to the front. Closer to the surface, the shear profile is also more unidirectional, leading the severe threat to be linear in nature along and north of the warm front with damaging winds and hail being the primary hazards.

Pivoting to Thursday afternoon, enhanced southerly flow ahead of the low pressure moving over central Iowa will support warm and moist air advection in the low levels and a medium chance (40-60%) of SBCAPE exceeding 2000 J/kg again, mainly south of Highway 20. However, there will be a strong gradient in bulk shear compared to the morning hours with 50-60 knots along Highway 20 and 30-40 knots along and south of I-80. This shear will also be at a 45-degree angle with the approaching cold front, being supportive for a mixed mode convection of supercells and linear structures. 100+ m2/s2 of 0- 1 km SRH is enough to support tornadic circulations in supercells and any QLCS, and low-level flow above the surface at 35-40 knots could easily be mixed down to produce damaging winds with strong storms.

In addition to severe weather, multiple rounds of storms with access to PWATs over 1.8 inches will be capable of producing localized flash flooding as well, especially in areas that received multiple inches of rainfall this week already.

Friday...With the cold frontal passage Thursday night, the flow throughout the atmosphere becomes unidirectional out of the westerly as high pressure anchors to our south. Cold air advection is forecasted to push highs back down into the upper 70s with mostly clear skies.

Saturday...Pleasant conditions do not last long as another shortwave rotates into the Dakotas Saturday afternoon. A cold front attached to an occluded low pressure system south of Hudson bay will be pushed into Iowa as a secondary low pressure deepens over Kansas. This will brings PoPs back up around 40-60%. A little bit of deju vu from Thursday with warm and moist air advection in the low levels, but the limited time with the southerly flow should only permit a low-to-medium chance (30-50%) for SBCAPE to get above 1000 J/kg. Bulk shear is also expected to be weaker than Thursday at only 35-40 knots. Therefore, there is a marginal chance at severe storms, but nothing like Wednesday and Thursday.

Sunday-Monday...As northerly flow returns in the low levels post cold front, highs return back to the 70s on Sunday. There is some model uncertainty on cloud cover as some lingering mid-level moisture could manifest into an altostratus deck. Regardless, Sunday will likely (60-80%) be a dry one. Monday is more iffy though as a trough digs into the Northern Rockies, producing a Front Range low pressure and developing a warm front. PoPs on Monday will be dependent on the frontal place and a potential mid-level F-gen band. Highs have a good chance (80-90%) of once again being below 80 degrees as cool air and cloud cover stick around.

AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/

Issued at 1250 PM CDT Tue Jun 9 2026

An isolated shower or storm possible this afternoon mainly south of I-80, otherwise mainly a VFR TAF as the lingering MVFR stratocu continues to lift or/and scatter out through mid afternoon. The light and variable sfc wind regime will look to become more southerly this evening and into the overnight, hopefully with enough speed to limit more fog production. There will be a late night chance for an isolated storm after midnight in developing WAA regime aloft, but not worth more than a 2 hour PROB30 mention in the potential convective window. A better chance for more storms may come late in the TAF period as scattered potentially strong storms move east acrs the area. Away from the storms, ambient sfc winds to get gusty on Wednesday from the southwest.

DVN WATCHES/WARNINGS/ADVISORIES

IA...Heat Advisory until 9 PM CDT this evening for IAZ076>078- 087>089-098-099. IL...Heat Advisory until 9 PM CDT this evening for ILZ024>026-034- 035. MO...Heat Advisory until 9 PM CDT this evening for MOZ009-010.